Process and apparatus for producing diesel with high cetane

ABSTRACT

A process and apparatus is provided to produce desulfurized diesel at low pressure with high cetane rating. A hydrotreated stream is stripped and fed to a saturation reactor. The saturated stream is stripped again and fractionated to provide diesel product. Unconverted oil may be hydrocracked and stripped with the saturated product.

FIELD

The field relates to a hydrocarbon conversion process and apparatus forthe production of diesel.

BACKGROUND

It has been recognized that due to environmental concerns and newlyenacted rules and regulations, saleable petroleum products must meetlower and lower limits on contaminates, such as sulfur and nitrogen. Newregulations require essentially complete removal of sulfur from liquidhydrocarbons that are used in transportation fuels, such as gasoline anddiesel. For example, ultra low sulfur diesel (ULSD) requires typicallyless than about 10 wppm sulfur.

Hydroprocessing is a process that contacts a selected feedstock andhydrogen-containing gas with suitable catalyst(s) in a reaction vesselunder conditions of elevated temperature and pressure. Hydrocrackingrefers to a process in which hydrocarbons crack in the presence ofhydrogen and catalyst to lower molecular weight hydrocarbons.Hydrocracking is a process used to crack hydrocarbon feeds such asvacuum gas oil (VGO) to diesel including kerosene and gasoline motorfuels. Hydrotreating is a type of hydroprocessing active for the removalof heteroatoms, such as sulfur and nitrogen, and saturating unsaturatedcompounds in the hydrocarbon feedstock.

Hydrotreating and hydrocracking converts sulfur on hydrocarbons tohydrogen sulfide and nitrogen on hydrocarbons to ammonia. Ammonia is acatalyst poison for hydroprocessing catalyst such as hydrocrackingcatalyst and saturation catalyst, particularly, noble metal saturationcatalyst. Hydrogen sulfide and ammonia gases are stripped from liquidhydrocarbon streams to prepare them for further catalytic processing andto provide fuel products with low sulfur.

At higher pressures, such as 12.4 MPa (1800 psig) to 17.2 MPa (2500psig), hydrotreating can also saturate aromatic compounds to increasethe cetane number of diesel produced from a hydrocarbonaceous feed or torender it more susceptible to hydrocracking However, at lower pressureshydrotreating catalyst is less effective in saturating aromatics. Highpressure processing is more expensive on capital and operational basesbecause it requires more robust metallurgy and compression systems.

There is a continuing need, therefore, for improved methods to producediesel product with lower sulfur content and higher cetane value atlower cost.

SUMMARY

In a process embodiment, a process is provided to produce dieselcomprising hydrotreating a hydrocarbonaceous feedstock with hydrogen ina hydrotreating reactor over a hydrotreating catalyst at conditionseffective to produce a hydrotreated stream. Light gases are strippedfrom the hydrotreated stream to provide a stripped hydrotreated stream.Aromatics in the stripped hydrotreated stream are saturated to produce asaturated stream. Light gases are stripped from the saturated stream toprovide a stripped saturated stream. Lastly, the stripped saturatedstream is fractionated to produce a diesel stream.

In an apparatus embodiment, an apparatus is provided to produce dieselcomprising a hydrotreating reactor for hydrotreating a hydrocarbonaceousfeedstock to produce a hydrotreated stream. A first stripping section isin communication with the hydrotreating reactor for stripping lightgases from the hydrotreated stream. A saturation reactor is incommunication with the first stripping section for saturating aromatics.A second stripping section is in communication with the saturationreactor for stripping light gases from a saturated stream. Lastly, afractionation column is in communication with the second strippingsection.

Other embodiments encompass further details of the apparatus andprocess.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a simplified process flow diagram of an embodiment of thepresent invention.

DEFINITIONS

The term “communication” means that material flow is operativelypermitted between enumerated components.

The term “downstream communication” means that at least a portion ofmaterial flowing to the subject in downstream communication mayoperatively flow from the object with which it communicates.

The term “upstream communication” means that at least a portion of thematerial flowing from the subject in upstream communication mayoperatively flow to the object with which it communicates.

The term “direct communication” means that flow from the upstreamcomponent enters the downstream component without undergoing acompositional change due to physical fractionation or chemicalconversion.

As used herein, the term “predominant” or “predominate” refers togreater than 50%, suitably greater than 75% and preferably greater than90%.

The term “column” means a distillation column or columns for separatingone or more components of different volatilities which may have areboiler on its bottom and a condenser on its overhead. Unless otherwiseindicated, each column includes a condenser on an overhead of the columnto condense and reflux a portion of an overhead stream back to the topof the column and, at a bottom of the column, an inert gas injection orreboiler to vaporize and send a portion of a bottoms stream back to thebottom of the column. Feeds to the columns may be preheated. The toppressure is the absolute pressure of the overhead vapor at the outlet ofthe column. The bottom temperature is the liquid bottom outlettemperature.

As used herein, the term “True Boiling Point” (TBP) means a test methodfor determining the boiling point of a material which corresponds toASTM D2892 for the production of a liquefied gas, distillate fractions,and residuum of standardized quality on which analytical data can beobtained, and the determination of yields of the above fractions by bothmass and volume from which a graph of temperature versus mass-%distilled is produced using fifteen theoretical plates in a column witha 5:1 reflux ratio.

As used herein, the term “diesel boiling range” means hydrocarbons inwhich at least 5 vol-% of the hydrocarbons boil at a temperature of noless than about 132° C. (270° F.) and no more than 95 vol-% of thehydrocarbons at a temperature of no more than about 399° C. (750° F.),preferably 377° C. (710° F.), using the True Boiling Point distillationmethod.

As used herein, the term “vacuum gas oil boiling range” meanshydrocarbons in which at least 5 vol-% of the hydrocarbons boil at atemperature of no less than about 315° C. (600° F.) and no more than 95vol-% of the hydrocarbons at a temperature of no more than about 566° C.(1050° F.) using the True Boiling Point distillation method.

The term “hydrotreat” generally refers to the saturation of double andtriple bonds and removal of heteroatoms (oxygen, sulfur, nitrogen andmetals) from heteroatomic compounds. Typically, to “hydrotreat” means totreat a hydrocarbon stream with hydrogen without making any substantialchange to the carbon backbone of the molecules in the hydrocarbon streamwith the corresponding production of water, hydrogen sulfide and ammoniafrom the heteroatoms in the heteroatomic compounds. Metals typicallyincorporate onto the catalyst when hydrotreated.

The term “hydrocrack” generally refers to the breaking down of highmolecular weight material into lower molecular weight material in thepresence of hydrogen gas and typically in the presence of a catalyst.For example, to “hydrocrack” means to split a hydrocarbon to form twohydrocarbon molecules.

DETAILED DESCRIPTION

Hydrotreating at lower pressures saves capital and operational costs butdoes not saturate aromatics sufficiently to boost cetane. We propose toprovide a noble metal saturation catalyst to provide the cetaneincrease, but it must operate in an environment free of noble metalcatalyst poisons. Consequently, the light materials are strippeddownstream of a hydrotreating reactor to remove such poisons upstream ofan aromatic saturation reactor. The saturated stream may also bestripped to remove hydrogen sulfide and ammonia upstream of a productfractionation column.

In one aspect, the processes and apparatuses described herein areparticularly useful for hydroprocessing a hydrocarbonaceous feedstockcontaining diesel or VGO boiling range hydrocarbons. Illustrativehydrocarbon feedstocks include hydrocarbonaceous streams havingcomponents initial boiling points above about 288° C. (550° F.), such asatmospheric gas oils, vacuum gas oils, deasphalted, vacuum, andatmospheric residua, hydrotreated or mildly hydrocracked residual oils,coker distillates, straight run distillates, solvent-deasphalted oils,pyrolysis-derived oils, high boiling synthetic oils, cycle oils, catcracker distillates, and the like. These hydrocarbonaceous feed stocksmay contain from about 0.1 to about 4 percent sulfur.

A preferred hydrocarbonaceous feedstock is a gas oil stream or otherhydrocarbon fraction predominately boiling at a temperature above about287° C. (550° F.) and below about 510° C. (950° F.).

Turning to the FIGURE, an exemplary integrated low-pressurehydroprocessing apparatus and process to provide low sulfur, high cetanediesel will be described in more detail. It will be appreciated by oneskilled in the art that various features of the above described process,such as pumps, instrumentation, heat-exchange and recovery units,condensers, compressors, flash drums, feed tanks, and other ancillary ormiscellaneous process equipment that are traditionally used incommercial embodiments of hydrocarbon conversion processes have not beendescribed or illustrated. It will be understood that such accompanyingequipment may be utilized in commercial embodiments of the flow schemesas described herein. Such ancillary or miscellaneous process equipmentcan be obtained and designed by one skilled in the art without undueexperimentation.

The FIGURE shows a process and apparatus 10 for producing a low sulfur,high cetane diesel stream. A make-up hydrogen gas stream in line 11 fromone or more make-up gas compressors 13 may be provided to a hydrogenline 15 along with a recycle gas stream in line 17 from a recycle gascompressor 150. The hydrogen line 15 may be split into three split lines16, 85 and 102. A hydrocarbonaceous feedstock is introduced in ahydrocarbonaceous feed line 12 and is preheated and combined with ahydrogen gas stream in a first split line 16 to provide an admixture ofthe hydrocarbonaceous feedstock and hydrogen in line 14.

The admixture of the hydrocarbonaceous feedstock and hydrogen in line 14is heated in a fired heater and fed to a first hydrotreating reactor 22in a hydrotreating reaction zone 20. The first hydrotreating reactor 22shown in the FIGURE may be accompanied by a second hydrotreating reactor24 in the hydrotreating reaction zone 20. More hydrotreating reactorsare contemplated. Each of the hydrotreating reactors 22, 24 may havejust one bed of hydrotreating catalyst 26 or have multiple hydrotreatingcatalyst beds 26, 28. A hydrogen quench stream 18 may bypass heaters andbe divided up and fed to the effluent from a hydrotreating catalyst bed26, 28 or a hydrotreating reactor 22, 24 to cool the hot hydrotreatedeffluent. A first hydrotreated stream exits the first hydrotreatingreactor 20 in line 23. One or both of the hydrotreating reactors 22, 24in the hydrotreating reaction zone 20 may be operated in a continuousliquid or gas phase. A hydrotreated stream 30 leaves the secondhydrotreating reactor 24 and the hydrotreating zone 20 in line 30.

In hydrotreating, hydrogen gas is contacted with hydrocarbonaceousfeedstock in the presence of suitable hydrotreating catalysts which areprimarily active for the removal of heteroatoms, such as sulfur andnitrogen from the hydrocarbon feedstock and saturation of unsaturatedhydrocarbons. In the hydrotreating reactor(s) 22, 24, conditions areeffective for hydrotreating reactions to predominate over any otherreaction to produce a hydrotreated stream in line 30. Suitablehydrotreating catalysts for use in the present invention are any knownconventional hydrotreating catalysts and include those which arecomprised of at least one Group VIII metal, preferably iron, cobalt andnickel, more preferably cobalt and/or nickel and at least one Group VImetal, preferably molybdenum and tungsten, on a high surface areasupport material, preferably alumina. Other suitable hydrotreatingcatalysts include zeolitic catalysts, as well as noble metal catalystswhere the noble metal is selected from palladium and platinum. It iswithin the scope of the present invention that more than one type ofhydrotreating catalyst be used in the same reaction vessel. The GroupVIII metal is typically present in an amount ranging from about 2 toabout 20 wt-%, preferably from about 4 to about 12 wt-%. The Group VImetal will typically be present in an amount ranging from about 1 toabout 25 wt-%, preferably from about 2 to about 25 wt-%.

Suitable hydrotreating reaction conditions include a temperature fromabout 371° C. (700° F.) to about 482° C. (900° F.), preferably fromabout 388° C. (730° F.) to about 460° C. (860° F.) and a liquid hourlyspace velocity of the fresh hydrocarbonaceous feedstock from about 0.1hr⁻¹ to about 10 hr⁻¹ with a hydrotreating catalyst or a combination ofhydrotreating catalysts. In an aspect, the hydrotreating reaction zoneis operated at a lower pressure than typical hydrotreaters such as apressure from about 3.5 MPa (gauge) (500 psig) to about 11.7 MPa (gauge)(1700 psig), preferably from about 9.0 MPa (gauge) (1300 psig) to about11.0 MPa (gauge) (1600 psig). In an aspect, hydrotreated effluent havinga lower organic sulfur and nitrogen concentration and an improved cetanenumber than that of the hydrocarbonaceous feedstock exits thehydrotreating reaction zone 20 in line 30 and enters a hydrotreatingseparation zone 110. However, at the lower pressure in the hydrotreatingreactor(s) 22, 24, saturation of olefins occurs, but saturation ofaromatic rings is limited. Consequently at the lower pressure of theapparatus and process, cetane uplift is not as great as at typicallyhigher pressures.

The hydrotreated stream in line 30 may be processed through a series ofvessels in the hydrotreating separation zone 110 to separate and flashoff hydrogen and lighter gases to remove hydrogen sulfide and ammoniafrom the hydrotreated stream and to provide a recycle hydrogen stream inline 142. Hydrogen sulfide and ammonia can poison downstreamhydroprocessing catalyst, particularly aromatic saturation catalyst.

The hydrotreated stream in line 30 may be cooled before entering ahydrotreating hot separator 120. In the hydrotreating hot separator 120,the hydrotreated stream is separated into a hot vaporous hydrotreatedstream comprising hydrogen in a hot separator overhead line 122 and ahot liquid hydrotreated stream in a hot separator bottoms line 124. Thehot liquid hydrotreated stream in the hot separator bottoms line 124 maybe stripped in the stripping column 42 of the stripping zone 40 or befurther flashed. The hydrotreating hot separator 120 operates at about177° C. (350° F.) to about 371° C. (700° F.) and the pressure of thehydrotreating reaction zone 20. The vaporous hydrotreated stream in thehot separator overhead line 122 may be joined by a wash water stream inline 126 to wash out ammonium hydrosulfides, cooled and enter the coldseparator 140.

The hot liquid hydrotreated stream in line 124 may be flashed in ahydrotreating hot flash drum 130 to provide a hot vaporous flash streamin a hot flash overhead line 132 and a hot liquid flash hydrotreatedstream in a hot flash bottoms line 134. The hydrotreating hot flash drum130 may be operated at the same temperature as the hydrotreating hotseparator 120 but at a lower pressure of between about 1.4 MPa (gauge)(200 psig) and about 3.1 MPa (gauge) (450 psig). The hot liquid flashhydrotreated stream in the hot flash bottoms line 134 may be stripped inthe stripping column 42 of the stripping zone 40.

A hydrotreating cold separator 140 is in downstream communication withthe hydrotreating hot separator overhead line 122 and the hydrotreatingreactor(s) 22, 24 of the hydrotreating reaction zone 20. In an aspect,the hydrotreating hot separator 120 and the hydrotreating hot flash drum130 can be dispensed with and the cold hydrotreating separator 140 willbe in direct, downstream communication with the hydrotreating reactor(s)22, 24 and receive the hydrotreating stream in line 30, directly. In thehydrotreating cold separator 140, the hot vaporous hydrotreated streamis separated into a cold vaporous stream comprising hydrogen in a coldseparator overhead line 142 and a cold liquid hydrotreated stream in acold separator bottoms line 144. The hydrotreating cold separator alsohas a boot for collecting an aqueous phase in line 146. The coldvaporous hydrotreated stream in line 142 may be scrubbed in a scrubber148 to remove hydrogen sulfide by amine absorption and recycled via arecycle gas compressor 150 to the hydrogen supply line 15. Thehydrotreating cold separator may be operated at about 15° C. (60° F.),preferably about 46° C. (115° F.), to about 63° C. (145° F.) and justbelow the pressure of the hydrotreating reaction zone 20 accounting forpressure drop in the lines therebetween to keep hydrogen and light gasessuch as hydrogen sulfide and ammonia in the overhead and normally liquidhydrocarbons in the bottoms. The hydrotreating cold separator 140 isoperated at a temperature below the temperature at which thehydrotreating hot separator 120 is operated. The cold liquidhydrotreated stream in the cold separator bottoms line 124 may bestripped in the stripping column 42 of the stripping zone 40 or befurther flashed.

In an aspect, the cold liquid hydrotreated stream in the hydrotreatingcold separator bottoms line 144 may be flashed in the hydrotreating coldflash drum 160 which may be operated at the same temperature as thehydrotreating cold separator 140 but at a lower pressure of betweenabout 1.4 MPa (200 psig) and about 3.5 MPa (gauge) (500 psig) to providea cold liquid flash hydrotreated stream in a cold flash bottoms line164. In an aspect, the hot vaporous flash stream in the hot flashoverhead line 132 may join the cold liquid hydrotreated stream in thecold separator bottoms line 144 and be flashed in the hydrotreating coldflash drum 160 together. The aqueous stream in line 146 from the boot ofthe hydrotreating cold separator may directed to the hydrotreating coldflash drum 160. A flash aqueous stream comprising sour water is removedfrom a boot in the hydrotreating cold flash drum 160 in line 166. A coldvaporous flash stream is removed in the cold flash overhead line 162.The cold liquid flash hydrotreated stream in cold flash bottoms line 164may be stripped in the stripping column 42 of the stripping zone 40.

Although hydrogen sulfide and ammonia in the gas phase are removed fromthe hydrotreated streams, they remain absorbed in the hydrocarbon liquidphase. Still further removal of these poisons from the hydrotreatedstream by stripping will be necessary for the hydrotreated stream to besuitable for contact with aromatic saturation catalyst.

The stripping zone 40 comprises a stripping column 42 in downstreamcommunication with the hydrotreating reaction zone 20. The strippingcolumn 42 strips light gases from the hydrotreated stream to provide astripped hydrotreated stream in a stripper bottoms line 46. In anaspect, the stripping column 42 strips the cold liquid flashhydrotreated stream in cold flash bottoms line 164 entering through afirst hydrotreated stream inlet 31. Alternatively, the stripping columnstrips cold liquid hydrotreated stream in the cold separator bottomsline 144 which may enter through the first hydrotreated stream inlet 31(not shown). Additionally or alternatively, the stripping column stripsthe hot liquid flash hydrotreated stream in hot flash bottoms line 134entering through a second hydrotreated stream inlet 32. Alternatively,the stripping column strips hot liquid hydrotreated stream in the hotseparator bottoms line 124 which may enter through the secondhydrotreated stream inlet 32 (not shown).

The stripping column 42 strips the hydrotreated stream with strippinggas to provide a light gas stream in the off-gas line 44 and a strippedhydrotreated stream in a bottoms line 46. In an embodiment, an overheadline 48 removes vapor from a top of the stripping column 42. The vaporfrom overhead line 48 is condensed and deposited in a receiver 50. Theoff-gas line 44 removes light gas from a top of the receiver 50, andunstabilized naphtha from a bottom of the receiver in line 52. Anaqueous phase may be removed from a boot in the receiver 50. At least aportion of the unstabilized naphtha may be refluxed to the fractionationcolumn 42, while unstabilized naphtha may be recovered in line 54 forfurther processing. The light gas can be scrubbed to remove gases fromthe fuel gas for further recovery and use which is not shown. The toppressure in the stripping column 42 ranges between about 621 kPa (gauge)(90 psig) and about 1034 kPa (gauge) (150 psig) and the bottomtemperature in the stripping column 42 ranges between about 210° andabout 307° C. if the feed in line 12 is predominantly a VGO boilingrange feed. Other bottom temperatures may be suitable for differentfeeds in line 12.

In an aspect, stripping column 42 may be a dividing wall strippingcolumn 42. A dividing wall 56 may divide the dividing wall strippingcolumn 42 into separate sections, a first stripping section 58 on afirst side and a second stripping section 60 on a second side of thedividing wall. In this aspect, the hydrotreated stream comprising one ofthe cold liquid hydrotreated stream and the cold liquid flashhydrotreated stream and perhaps one of the hot liquid hydrotreatedstream and the hot liquid flash saturated stream is fed is fed to thefirst stripping section 58 of the dividing wall stripping column 42through a first hydrotreated stream inlet 31, so the first strippingsection 58 is in downstream communication with the hydrotreating reactor22 or hydrotreating reactor(s) 22, 24 in the hydrotreating reaction zone20. The stripped hydrotreated stream is recovered at a bottom of thefirst stripping section 58 of the dividing wall stripping column 42 inthe first bottoms line 46. In an aspect, the dividing wall 56 extends tothe bottom of the dividing wall fractionation column 42 and is attachedand sealed to a bottom and inner walls of the dividing wall column toprevent fluid communication between the first stripping section 58 onthe first side and the second stripping section 60 on the second side atany location below a top of the dividing wall 56. The cold liquid flashhydrotreated stream or the cold liquid hydrotreated stream is fed to thefirst side 58 at the first hydrotreated stream inlet 31 located below atop of the dividing wall 56. Additionally, the hot liquid flashhydrotreated stream or the hot liquid hydrotreated stream may be fed tothe first side 58 at the second hydrotreated stream inlet 32 locatedbelow a top of the dividing wall 56.

A top of the dividing wall 56 may be spaced from a top of the strippingcolumn 42, so gases in the overhead of the stripping column 42 maycommunicate from a first stripping section 58 with the second strippingsection 60 and vice versa. A single overhead line 48 may remove vaporfrom the first stripping section 58 and the second stripping section 60of the stripping column 42. The first hydrotreated stream inlet 31 andthe second hydrotreated stream inlet 32 to the first stripping section58 are at an elevation lower than a top of the dividing wall 56. Thefirst hydrotreated stream inlet 31 is at a higher elevation than thesecond hydrotreated stream inlet 32.

A first stripping stream of inert gas in a first stripping line 33comprising an inert gas is injected into a bottom of the first strippingsection 58 through a first stripping stream inlet 34 to strip lightgases from the down-flowing liquid hydrotreated stream. The inert gasmay be hydrogen or steam, but steam is preferred. The first hydrotreatedstream inlet 31 and the second hydrotreated stream inlet 32 and a firststripping stream inlet 34 are in the first stripping section 58. Astripped hydrotreated stream may exit the first stripping section 58through a first outlet 43 in the first bottoms line 46, which is locatedbelow the first hydrotreated stream inlet 31 and the second hydrotreatedstream inlet 32 to the first stripping section 58 at a bottom of thestripping column 42. The bottom temperature in the first strippingsection 58 of the dividing wall fractionation column 42 ranges betweenabout 285° and about 307° C. if the feed in line 12 is predominantly aVGO boiling range feed.

At the lower pressures in the hydrotreating reactor, the cetane value ofdiesel in the hydrotreated stream in line 30 and the strippedhydrotreated stream in bottoms line 46 may not be sufficiently high.Therefore, to boost the cetane value, the stripped hydrotreated streammust be further saturated. Essentially all of the ammonia and hydrogensulfide are removed as off-gas from the stripping column 42, so thestripped hydrotreated feed in the first bottoms line 46 can be saturatedin the saturation reactor 80 without poisoning the noble metal catalystthat is most effective for saturating aromatic compounds.

The apparatus and process 10 comprises a saturation reactor 80 indownstream communication with the first stripping section 58 of thestripping column 42. A second hydrogen split line 85 provides asaturation hydrogen stream to the stripped hydrotreated stream in thebottoms line 46 to present a saturation feed stream in saturation feedline 86. The saturation feed stream may be heated in a fired heater andfed to the saturation reactor 80. In the saturation reactor, thearomatics in the stripped hydrotreated stream are saturated over asaturation catalyst at saturation conditions to produce cyclo-aliphaticsthereby increasing the cetane rating of the diesel. Olefins are alsosaturated and other hydrotreating reactions occur in the saturationreactor 80. In the saturation reactor, hydrotreating reactionspredominate over other reactions.

The saturation reactor 80 in the FIGURE is shown to comprise one reactorvessel and three catalyst beds 81, 82 and 83. More reactor vessels andmore or less catalyst beds may be used as the saturation reactor 80. Ahydrogen quench stream 87 may bypass heaters and be divided up and fedto the effluent from a saturation catalyst bed 81, 82, 83 or thesaturation reactor 80 to cool the hot saturation effluent.

Suitable saturation catalysts for use in the present invention are anyknown conventional hydrotreating catalysts and include those which arecomprised of at least one Group VIII metal, preferably iron, cobalt andnickel, more preferably cobalt and/or nickel and at least one Group VImetal, preferably molybdenum and tungsten, on a high surface areasupport material, preferably alumina. Other suitable hydrotreatingcatalysts include zeolitic catalysts. A preferred saturation catalyst isa noble metal catalyst for which the noble metal is selected frompalladium and platinum. It is within the scope of the present inventionthat more than one type of saturation catalyst be used in the samesaturation reactor 80. The noble metal is typically present in an amountranging from 0.1 to 5 wt-%, preferably from 0.2 to 1.0 wt-% in thesaturation catalyst.

Preferred saturation reaction conditions include a temperature from 315°C. (600° F.) to 427° C. (800° F.) and preferably 343° C. (650° F.) to377° C. (710° F.). Saturation reactor pressure is usually greater, butin the low pressure environment of the apparatus and process 10, thepressure in the saturation reactor may be from about 6.9 MPa (gauge)(1000 psig) to about 10.3 MPa (gauge) (1500 psig), preferably from about7.6 MPa (1100 psig) to about 9.7 MPa (1400 psig), a liquid hourly spacevelocity of the fresh hydrocarbonaceous feedstock from about 0.5 hr⁻¹ toabout 4 hr⁻¹, preferably from about 1.5 to about 3.5 hr⁻¹, and ahydrogen rate of about 168 Nm³/m³ oil (1,000 scf/bbl), to about 1,011Nm³/m³ oil (6,000 scf/bbl), preferably about 168 Nm³/m³ oil (1,000scf/bbl) to about 674 Nm³/m³ oil (4,000 scf/bbl).

Before describing the recovery of the saturation stream, description ofthe hydrocracking aspect of the process and apparatus will be describedbecause the saturation stream and the hydrocracking stream may beprocessed together.

A hydrocarbon stream which may be a saturated unconverted oil stream ina fractionator bottoms line 100 may be fed to the hydrocracking reactor180. It should be understood that the hydrocracking reactor 180 isoptional.

In an embodiment, the hydrocracking reactor 180 is in downstreamcommunication with the saturation reactor 80, the second strippingsection 60 of the stripping column 42 and the fractionation column 70.The hydrocarbon stream in the fractionator bottoms line 100 is preheatedand combined with a hydrogen gas stream from the third split line 102.The hydrogen gas stream from line 102 is admixed with the hydrocarbonstream in the fractionator bottoms line 100 to provide an admixture ofthe hydrocarbon stream and hydrogen in line 104.

The admixed stream in line 104 is heated in a fired heater and fed tothe hydrocracking reactor 180. The hydrocracking reactor 180 may includemore than one reactor vessel. The hydrocracking reactor 180 shown in theFIGURE has only one reactor vessel. More hydrocracking reactor vesselsare contemplated. The hydrocracking reactor 180 may have just one bed186 of hydrocracking catalyst or have multiple hydrocracking catalystbeds 186, 187 and 188. A hydrocracked stream exits the hydrocrackingreactor 180 in line 182. A hydrogen quench stream 103 may bypass heatersand be divided up and fed to the effluent from a hydrocracking catalystbed 186, 187, 188 or hydrocracking reactor 180 to cool the hothydrocracked effluent.

In an aspect, the hydrocracked stream in line 182 may join thesaturation stream in line 88 and be jointly processed together in asaturation separation zone 210 before entering the second strippingsection 60 of the stripping column 42 in the stripping zone 40 together.The second stripping section 60 is in downstream communication with thesaturation reactor 80 and the hydrocracking reactor 180.

In the hydrocracking reactor 180, the hydrocarbon stream in line 104 ishydrocracked with hydrogen over a hydrocracking catalyst at conditionseffective to produce a hydrocracked stream in line 182. Hydrocrackingreactions involve the cracking of carbon-carbon bonds. In thehydrocracking reactor 180, hydrocracking reactions predominate overother reactions.

In one aspect, for example, when a balance of middle distillate andgasoline is preferred in the converted product, mild hydrocracking maybe performed in the hydrocracking reactor 180 with hydrocrackingcatalysts that utilize amorphous silica-alumina bases or low-levelzeolite bases combined with one or more Group VIII or Group VIB metalhydrogenating components. In another aspect, when middle distillate issignificantly preferred in the converted product over gasolineproduction, partial or full hydrocracking may be performed in thehydrocracking reactor 180 with a catalyst which comprises, in general,any crystalline zeolite cracking base upon which is deposited a GroupVIII metal hydrogenating component. Additional hydrogenating componentsmay be selected from Group VIB for incorporation with the zeolite base.

The zeolite cracking bases are sometimes referred to in the art asmolecular sieves and are usually composed of silica, alumina and one ormore exchangeable cations such as sodium, magnesium, calcium, rare earthmetals, etc. They are further characterized by crystal pores ofrelatively uniform diameter between about 4 and about 14 Angstroms(10⁻¹⁰ meters). It is preferred to employ zeolites having a relativelyhigh silica/alumina mole ratio between about 3 and about 12. Suitablezeolites found in nature include, for example, mordenite, stilbite,heulandite, ferrierite, dachiardite, chabazite, erionite and faujasite.Suitable synthetic zeolites include, for example, the B, X, Y and Lcrystal types, e.g., synthetic faujasite and mordenite. The preferredzeolites are those having crystal pore diameters between about 8-12Angstroms (10⁻¹⁰ meters), wherein the silica/alumina mole ratio is about4 to 6. One example of a zeolite falling in the preferred group issynthetic Y molecular sieve.

The naturally occurring zeolites are normally found in a sodium form, analkaline earth metal form, or mixed forms. The synthetic zeolites arenearly always prepared first in the sodium form. In any case, for use asa cracking base it is preferred that most or all of the originalzeolitic monovalent metals be ion-exchanged with a polyvalent metaland/or with an ammonium salt followed by heating to decompose theammonium ions associated with the zeolite, leaving in their placehydrogen ions and/or exchange sites which have actually beendecationized by further removal of water. Hydrogen or “decationized” Yzeolites of this nature are more particularly described in U.S. Pat. No.3,130,006.

Mixed polyvalent metal-hydrogen zeolites may be prepared byion-exchanging first with an ammonium salt, then partially backexchanging with a polyvalent metal salt and then calcining. In somecases, as in the case of synthetic mordenite, the hydrogen forms can beprepared by direct acid treatment of the alkali metal zeolites. In oneaspect, the preferred cracking bases are those which are at least about10 percent, and preferably at least about 20 percent,metal-cation-deficient, based on the initial ion-exchange capacity. Inanother aspect, a desirable and stable class of zeolites is one whereinat least about 20 percent of the ion exchange capacity is satisfied byhydrogen ions.

The active metals employed in the preferred hydrocracking catalysts ofthe present invention as hydrogenation components are those of GroupVIII, i.e., iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium,iridium and platinum. In addition to these metals, other promoters mayalso be employed in conjunction therewith, including the metals of GroupVIB, e.g., molybdenum and tungsten. The amount of hydrogenating metal inthe catalyst can vary within wide ranges. Broadly speaking, any amountbetween about 0.05 percent and about 30 percent by weight may be used.In the case of the noble metals, it is normally preferred to use about0.05 to about 2 wt-%.

The method for incorporating the hydrogenating metal is to contact thebase material with an aqueous solution of a suitable compound of thedesired metal wherein the metal is present in a cationic form. Followingaddition of the selected hydrogenating metal or metals, the resultingcatalyst powder is then filtered, dried, pelleted with added lubricants,binders or the like if desired, and calcined in air at temperatures of,e.g., about 371° C. (700° F.) to about 648° C. (1200° F.) in order toactivate the catalyst and decompose ammonium ions. Alternatively, thebase component may first be pelleted, followed by the addition of thehydrogenating component and activation by calcining.

The foregoing catalysts may be employed in undiluted form, or thepowdered catalyst may be mixed and copelleted with other relatively lessactive catalysts, diluents or binders such as alumina, silica gel,silica-alumina cogels, activated clays and the like in proportionsranging between about 5 and about 90 wt-%. These diluents may beemployed as such or they may contain a minor proportion of an addedhydrogenating metal such as a Group VIB and/or Group VIII metal.Additional metal promoted hydrocracking catalysts may also be utilizedin the process of the present invention which comprises, for example,aluminophosphate molecular sieves, crystalline chromosilicates and othercrystalline silicates. Crystalline chromosilicates are more fullydescribed in U.S. Pat. No. 4,363,718.

By one approach, the hydrocracking conditions may include a temperaturefrom about 343° C. (650° F.) to about 427° C. (800° F.), preferably 379°C. (715° F.) to about 399° C. (750° F.). If mild hydrocracking isdesired, conditions may include a temperature from about 315° C. (600°F.) to about 441° C. (825° F.). The pressure in the hydrocrackingreactor may be from about 6.9 MPa (gauge) (1000 psig) to about 10.3 MPa(gauge) (1500 psig), preferably from about 7.6 MPa (1100 psig) to about9.7 MPa (1400 psig). The liquid hourly space velocity (LHSV) in thehydrocracking reactor may be from about 0.5 to about 5.0 hr⁻¹ and ahydrogen rate of about 421 Nm³/m³ oil (2,500 scf/bbl) to about 2,527Nm³/m³ oil (15,000 scf/bbl.)

The saturated stream in line 88 may be joined by the hydrocracked streamin line 110 and may be cooled before entering the saturation separationzone 210 as a joint stream in joint line 90. It should be understoodthat the saturated stream in line 88 may be separated in the saturationseparation zone and further processed by itself or jointly with thehydrocracked stream in line 182. For purposes of description, theprocessing of the saturated stream will be described as if it is jointlyprocessed with the hydrocracked stream but processing of the saturatedstream without the hydrocracked stream is contemplated.

The joint stream including the saturated stream and the hydrocrackedstream may enter a saturation hot separator 220. In the saturation hotseparator 220 the joint stream is separated into a hot vaporoussaturated stream comprising hydrogen in a hot separator overhead line222 and a hot liquid saturated stream in a hot separator bottoms line224. The saturation hot separator 220 operates at about 177° C. (350°F.) to about 371° C. (700° F.) and at the same pressure as thesaturation reactor 80 and/or the hydrocracking reactor 180. The vaporoussaturated stream in the hot separator overhead line 222 may enter asaturation cold separator 240. The hot liquid saturated stream in thehot separator bottoms line 224 may be stripped in the stripping zone 40or be further flashed.

The hot liquid saturated stream in line 224 may be flashed in asaturation hot flash drum 230 to provide a hot vaporous flash saturatedstream in a hot flash overhead line 232 and a hot liquid flash saturatedstream in a hot flash bottoms line 234. The saturation hot flash drum230 may be operated at the same temperature as the saturation hotseparator 220 but at a lower pressure of between about 1.4 MPa (gauge)(200 psig) and about 3.5 MPa (gauge) (500 psig). The hot liquid flashsaturated stream in the hot flash bottoms saturated stream may bestripped in the stripping column 42.

The saturation cold separator 240 may be in downstream communicationwith the saturation hot separator overhead line 222 and the saturationreactor 80 and/or the hydrocracking reactor 180. In an aspect, thesaturation hot separator 220 and the saturation hot flash drum 230 canbe dispensed with and the cold saturation separator 240 will be indirect, downstream communication with the saturation reactor 80 andperhaps the hydrocracking reactor 180 and receive the saturation streamin line 88 or in the joint stream 90, directly. In the saturation coldseparator 240, the hot vaporous saturated stream is separated into acold vaporous saturated stream comprising hydrogen in a cold separatoroverhead line 242 and a cold liquid saturated stream in a cold separatorbottoms line 244. The saturation cold separator also has a boot forcollecting an aqueous phase in line 246. The cold vaporous saturatedstream in line 242 may be recycled via a recycle gas compressor 150 tothe hydrogen line 15. The cold vaporous saturated stream in line 242 maybypass the scrubber 148 in route to the recycle gas compressor 150because the saturation feed in the first bottoms line 46 to thesaturation reactor 80 and the hydrocarbon feed in the fractionationbottoms line 100 to the hydrocracking reactor 180 have already beenstripped to remove most of the sulfur and nitrogen that could generatehydrogen sulfide and ammonia. The saturation cold separator may beoperated at about 15° C. (60° F.), preferably about 46° C. (115° F.), toabout 63° C. (145° F.) and just below the pressure of the saturationreactor 80 and/or the hydrocracking reactor 180 accounting for pressuredrop in the lines therebetween to keep hydrogen and light gases in theoverhead and normally liquid hydrocarbons in the bottoms. The saturationcold separator 240 is operated at a temperature below the temperature atwhich the saturation hot separator 220 is operated. The cold liquidsaturated stream in the cold separator bottoms line 244 may be strippedin the stripping zone 40 or be further flashed.

In an aspect, the cold liquid saturated stream in the cold separatorbottoms line 244 may be flashed in the saturation cold flash drum 260which may be operated at the same temperature as the saturation coldseparator 240 but at a lower pressure of between about 1.4 MPa (200psig) and about 3.5 MPa (gauge) (500 psig) to provide a cold liquidflash saturated stream in a cold flash bottoms line 264. In an aspect,the hot vaporous flash saturated stream in the hot flash overhead line232 may join the cold liquid saturated stream in the cold separatorbottoms line 244 and be flashed in the saturation cold flash drum 260together. The aqueous stream in line 246 from the boot of the saturationcold separator may directed to the saturation cold flash drum 260. Aflash aqueous stream comprising sour water is removed from a boot of thesaturation cold flash drum 260 in line 266. A cold vaporous flashsaturated stream is removed in the cold flash overhead line 262. Thecold liquid flash saturated stream in cold flash bottoms line 264 may bestripped in the stripping zone 40.

The stripping column 42 in the stripping zone 40 strips light gases fromthe saturated stream to provide a stripped saturated stream. Thestripping column 42 may also strip light gases and from the hydrocrackedstream to produce a stripped hydrocracked stream. In an aspect, thestripping column strips light gases from the hydrocracked stream and thesaturated stream together to produce a joint stripped stream comprisingthe stripped saturated stream and the stripped hydrocracked stream in asecond bottoms line 98.

In an aspect, the stripping column 42 strips the cold liquid flashsaturated stream in cold flash bottoms line 264 entering through a firstsaturation stream inlet 97. Alternatively, the stripping column stripscold liquid saturated stream in the cold separator bottoms line 244which may enter through the first saturation stream inlet 97 (notshown). Additionally or alternatively, the stripping column strips thehot liquid flash saturated stream in hot flash bottoms line 234 enteringthrough second saturation stream inlet 91. Alternatively, the strippingcolumn strips hot liquid saturated stream in the hot separator bottomsline 224 which may enter through the second saturation stream inlet 91(not shown). The stripping column 42 strips the hydrotreated stream withstripping gas to provide a light gas stream in the off-gas line 44 and astripped saturated stream in a bottoms line 98. In an aspect, thestripping column 42 is a dividing wall column, and the saturated streamcomprising one of the cold liquid saturated stream and the cold liquidflash saturated stream and perhaps one of the hot liquid saturatedstream and the hot liquid flash saturated stream are fed to the secondstripping section 60 on a second side of the dividing wall 56 in thedividing wall column 42, so the second side of the dividing wall columnis in downstream communication with the saturation reactor 80. Thesaturated stream may include a hydrocracked stream in an aspect.Additionally, the second stripping section 60 may be in downstreamcommunication with the hydrocracking reactor 180, so the saturatedstream is fed to the second stripping section 60 on a second side of thedividing wall 56 in the dividing wall column 42 jointly with thehydrocracked stream. The first stripping section 58 and said secondstripping section 60 are in a single stripping column 42 with thedividing wall 56 in between. In other words, the first stripping section58 is separated from the second stripping section 60 by the dividingwall 56 in the stripping column 42. The dividing wall 56 has a lower endattached to a bottom of the stripping column 42, and the dividing wallhas an upper end that is spaced apart from a top of the strippingcolumn. Light gases may be stripped from the hydrotreated stream and thesaturated stream and perhaps the hydrocracked stream in the singlestripping column 42.

In an aspect, the dividing wall 56 extends to the bottom of the dividingwall fractionation column 42 and is sealed to the bottom and sides ofthe dividing wall column to prevent communication between the firstsection 58 and the second stripping section 60 at any location below atop of the dividing wall 56. The dividing wall 56 isolates liquid in thehydrotreated stream entering through the first hydrotreating inlet 31and/or the second hydrotreating inlet 32 from liquid in the saturatedstream an perhaps the hydrocracked stream entering through the firstsaturation stream inlet 97 and/or the second saturation stream inlet 91while stripping light gases from the hydrotreated stream and thesaturated stream. The first saturation stream inlet 97 and the secondsaturation stream inlet 91 to the second stripping section 60 are at anelevation lower than a top of the dividing wall 56. The first saturationstream inlet 97 is at a higher elevation than the second saturationstream inlet 91.

A second stripping stream of inert gas in a second stripping line 96 isinjected through a second stripping stream inlet 95 into a bottom of thesecond stripping section 60 to strip gaseous components from the downflowing saturated stream. The second stripping stream does notcommunicate with the first stripping stream 33 fed to the firststripping section 58 before the second stripping stream strips thesaturated stream. The first saturated stream inlet 97 and the secondsaturated stream inlet 91 and a second stripping stream inlet 95 are inthe second stripping section 60. The saturated stream is fed to thesecond stripping section 60 below a top of the dividing wall 56. Thehydrocracked stream may also be fed jointly with the saturated stream tothe second stripping section 60 below a top of the dividing wall 56.

The inert gas may be hydrogen or steam, but steam is preferred. Thebottom temperature in the second stripping section 60 of the dividingwall fractionation column 42 ranges between about 200 and about 250° C.A stripped saturate stream is recovered from a second bottoms line 98exiting through a second bottoms outlet 99 from the second strippingsection 60 of the stripping column 42. A stripped hydrocracked streammay also be recovered with the stripped saturated stream as a jointstripped stream in the bottoms line 98. Light gases stripped from thehydrotreated stream in the first stripper section 58 communicate withlight gases stripped from the saturate stream in the second strippersection 60 and may be withdrawn in the same overhead line 48.

A fractionation column 70 fractionates the stripped saturated stream andperhaps the stripped hydrocracked stream to produce a diesel stream inline 94. The product diesel stream may have less than 50 wppm sulfur andpreferably less than 10 wppm sulfur. The product diesel stream also willhave a cetane number of at least 45 and preferably at least 50. Thefractionation column 70 is in downstream communication with the secondstriping section 60 of the stripping column 42. In an aspect, thefractionation column fractionates a joint stripped stream comprising thehydrocracked stream and the saturated stream together to produce thediesel stream in line 94. An overhead line 72 from the fractionationcolumn 70 may be condensed and deposited in a receiver 74 to yield anaphtha stream 76. A portion of the naphtha stream may be refluxed tothe fractionation column 70 and the other portion recovered as productor further processed in line 78. A saturated unconverted oil stream suchas VGO may be recovered from a bottom of the fractionation column inbottoms line 100 which may be an excellent feedstock to an FCC unit or ahydrocracking unit.

In the FIGURE, the saturated unconverted oil stream may be fed to thehydrocracking reactor as the hydrocarbon stream in the fractionationbottoms line 100. The hydrocracking reactor 180 may be in downstreamcommunication with the fractionation bottoms line 100 of thefractionation column 70. A fractionated kerosene stream may be recoveredfrom the fractionation column 70 as a side cut in line 92 and afractionated diesel stream may be recovered from the fractionationcolumn as a side cut in line 94. The fractionation column 70 may beheated by an inert stripping stream such as steam fed through line 93.The top pressure in the fractionator column 70 ranges between about 0kPa (gauge) (0 psig) and about 206 kPa (gauge) (30 psig) and the bottomtemperature in the fractionator column 70 ranges between about 300 andabout 350° C.

A first embodiment of the invention is a process to produce dieselcomprising hydrotreating a hydrocarbonaceous feedstock with hydrogen ina hydrotreating reactor over a hydrotreating catalyst at conditionseffective to produce a hydrotreated stream; stripping light gases fromthe hydrotreated stream to provide a stripped hydrotreated stream;saturating aromatics in the stripped hydrotreated stream to produce asaturated stream; stripping light gases from the saturated stream toprovide a stripped saturated stream and fractionating the strippedsaturated stream to produce a diesel stream. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the first embodiment in this paragraph, further comprisingisolating liquid in the hydrotreated stream from liquid in the saturatedstream while stripping light gases from the hydrotreated stream andstripping light gases from the saturated stream. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the first embodiment in this paragraph, further comprisingstripping light gases from the hydrotreated stream and stripping lightgases from the saturated stream in a single stripping column. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the first embodiment in this paragraph,wherein the single stripping column includes a dividing wall and thehydrotreated stream is fed to a first side of the dividing wall in thedividing wall column and the saturated stream is fed to a second side ofthe dividing wall. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the first embodiment inthis paragraph, further comprising stripping the hydrotreated streamwith a first stripping stream and stripping the saturated stream with asecond stripping stream that does not communicate with the firststripping stream before the second stripping stream strips the saturatestream. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the first embodiment in thisparagraph, further comprising hydrotreating the hydrocarbonaceous feedat a pressure of about 9 MPa to about 11 MPa (gauge). An embodiment ofthe invention is one, any or all of prior embodiments in this paragraphup through the first embodiment in this paragraph, further comprisinghydrocracking a hydrocarbon stream with hydrogen in a hydrocrackingreactor over a hydrocracking catalyst at conditions effective to producea hydrocracked stream. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the first embodimentin this paragraph further comprising stripping light gases from thehydrocracked stream to produce a stripped hydrocracked stream andfractionating the stripped hydrocracked stream to produce the dieselstream. An embodiment of the invention is one, any or all of priorembodiments in this paragraph up through the first embodiment in thisparagraph further comprising stripping light gases from the hydrocrackedstream and the saturated stream together to produce a joint strippedstream comprising the stripped saturated stream and the strippedhydrocracked stream and fractionating the joint stripped stream toproduce the diesel stream. An embodiment of the invention is one, any orall of prior embodiments in this paragraph up through the firstembodiment in this paragraph producing an unconverted oil stream in thefractionation step to provide the hydrocarbon stream.

A second embodiment of the invention is a process to produce dieselcomprising hydrotreating a hydrocarbonaceous feedstock with hydrogen ina hydrotreating reactor over a hydrotreating catalyst at conditionseffective to produce a hydrotreated stream; stripping light gases fromthe hydrotreated stream to provide a stripped hydrotreated stream;saturating aromatics in the stripped hydrotreated stream to produce asaturated stream; hydrocracking a hydrocarbon stream with hydrogen in ahydrocracking reactor over a hydrocracking catalyst at conditionseffective to produce a hydrocracked stream; and stripping light gasesfrom the saturated stream and the hydrocracked stream to provide a jointstripped stream comprising a stripped saturated stream and a strippedhydrocracked stream. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the second embodimentin this paragraph, further comprising fractionating the joint strippedstream to produce a diesel stream. An embodiment of the invention isone, any or all of prior embodiments in this paragraph up through thesecond embodiment in this paragraph, further comprising isolating liquidin the hydrotreated stream from liquid in the saturated stream and thehydrocracked stream while stripping light gases from the hydrotreatedstream and stripping light gases from the saturated stream and thehydrocracked stream. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the second embodimentin this paragraph, further comprising stripping light gases from thehydrotreated stream and stripping light gases from the saturated streamand the hydrotreated stream in a single stripping column. An embodimentof the invention is one, any or all of prior embodiments in thisparagraph up through the second embodiment in this paragraph, whereinthe single stripping column includes a dividing wall and thehydrotreated stream is fed to a first side of the dividing wall in thedividing wall column and the saturated stream is fed to a second side ofthe dividing wall. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the second embodiment inthis paragraph, further comprising producing an unconverted oil streamin the fractionation step to provide the hydrocarbon stream. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the second embodiment in this paragraph,further comprising stripping the hydrotreated stream with a firststripping stream and stripping the saturated stream and the hydrocrackedstream with a second stripping stream that does not communicate with thefirst stripping stream before the second stripping stream strips thesaturate stream and the hydrocracked stream. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the second embodiment in this paragraph, wherein light gasesstripped from the hydrotreated stream communicate with light gasesstripped from the saturate stream and the hydrocracked stream.

A third embodiment of the invention is a process to produce dieselcomprising hydrotreating a hydrocarbonaceous feedstock with hydrogen ina hydrotreating reactor over a hydrotreating catalyst at conditionseffective to produce a hydrotreated stream; stripping light gases fromthe hydrotreated stream to provide a stripped hydrotreated stream;saturating aromatics in the stripped hydrotreated stream to produce asaturated stream; hydrocracking a hydrocarbon stream with hydrogen in ahydrocracking reactor over a hydrocracking catalyst at conditionseffective to produce a hydrocracked stream; stripping light gases fromthe saturated stream and the hydrocracked stream to provide a jointstripped stream comprising a stripped saturated stream and a strippedhydrocracked stream; and fractionating the joint stripped stream toproduce a diesel stream. An embodiment of the invention is one, any orall of prior embodiments in this paragraph up through the thirdembodiment in this paragraph, further comprising producing anunconverted oil stream in the fractionation step to provide thehydrocarbon stream.

A fourth embodiment of the invention is an apparatus to produce dieselcomprising a hydrotreating reactor for hydrotreating a hydrocarbonaceousfeedstock to produce a hydrotreated stream; a first stripping section incommunication with the hydrotreating reactor for stripping light gasesfrom the hydrotreated stream; a saturation reactor in communication withthe first stripping section for saturating aromatics; a second strippingsection in communication with the saturation reactor for stripping lightgases from a saturated stream; and a fractionation column incommunication with the second stripping section. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the fourth embodiment in this paragraph, wherein the firststripping section and the second stripping section are in a singlestripping column. An embodiment of the invention is one, any or all ofprior embodiments in this paragraph up through the fourth embodiment inthis paragraph, wherein the first stripping section is separated fromthe second stripping section by a dividing wall in the stripping column.An embodiment of the invention is one, any or all of prior embodimentsin this paragraph up through the fourth embodiment in this paragraph,wherein the dividing wall has a lower end attached to a bottom of thestripping column and the dividing wall has an upper end that is spacedapart from a top of the stripping column. An embodiment of the inventionis one, any or all of prior embodiments in this paragraph up through thefourth embodiment in this paragraph, further comprising a hydrotreatedstream inlet and a first stripping stream inlet in the first strippingsection and a saturated stream inlet and a second stripping stream inletin the second stripping section. An embodiment of the invention is one,any or all of prior embodiments in this paragraph up through the fourthembodiment in this paragraph, further comprising a single overhead linefrom the stripping column. An embodiment of the invention is one, any orall of prior embodiments in this paragraph up through the fourthembodiment in this paragraph, wherein the saturation reactor is incommunication with the first stripping section. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the fourth embodiment in this paragraph wherein thefractionation column in communication with the second stripping section.An embodiment of the invention is one, any or all of prior embodimentsin this paragraph up through the fourth embodiment in this paragraphfurther comprising a hydrocracking reactor in communication with thefractionation column. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the fourth embodimentin this paragraph wherein the second stripping section is incommunication with the hydrocracking reactor.

A fifth embodiment of the invention is an apparatus to produce dieselcomprising a hydrotreating reactor for hydrotreating a hydrocarbonaceousfeedstock to produce a hydrotreated stream; a first stripping section incommunication with the hydrotreating reactor for stripping light gasesfrom the hydrotreated stream; a saturation reactor in communication withthe stripping column for saturating aromatics; a second strippingsection in communication with the saturation reactor for stripping lightgases from a saturated stream; and a hydrocracking reactor incommunication with the stripping column. An embodiment of the inventionis one, any or all of prior embodiments in this paragraph up through thefifth embodiment in this paragraph, wherein the first stripping sectionand the second stripping section are in a single stripping column. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the fifth embodiment in this paragraph,wherein the first stripping section is separated from the secondstripping section by a dividing wall in the stripping column; thedividing wall having a lower end attached to a bottom of the strippingcolumn and the dividing wall has an upper end that is spaced apart fromthe top of the stripping column. An embodiment of the invention is one,any or all of prior embodiments in this paragraph up through the fifthembodiment in this paragraph, wherein the saturation reactor is incommunication with the first stripping section and the hydrocrackingreactor is in communication with the second stripping section. Anembodiment of the invention is one, any or all of prior embodiments inthis paragraph up through the fifth embodiment in this paragraph furthercomprising a fractionation column in communication with the secondstripping section and the hydrocracking reactor in communication withthe fractionation column. An embodiment of the invention is one, any orall of prior embodiments in this paragraph up through the fifthembodiment in this paragraph wherein the second stripping section is indownstream communication with the hydrocracking reactor and thesaturation reactor.

A sixth embodiment of the invention is an apparatus to produce dieselcomprising a hydrotreating reactor for hydrotreating a hydrocarbonaceousfeedstock to produce a hydrotreated stream; a first stripping section incommunication with the hydrotreating reactor for stripping light gasesfrom the hydrotreated stream; a saturation reactor in communication withthe stripping column for saturating aromatics; a second strippingsection in communication with the saturation reactor for stripping lightgases from a saturated stream; a fractionation column in communicationwith the stripping column; and a hydrocracking reactor in communicationwith the fractionation column. An embodiment of the invention is one,any or all of prior embodiments in this paragraph up through the sixthembodiment in this paragraph, wherein the first stripping section andthe second stripping section are in a single stripping column and thefirst stripping section is separated from the second stripping sectionby a dividing wall in the stripping column. An embodiment of theinvention is one, any or all of prior embodiments in this paragraph upthrough the sixth embodiment in this paragraph, wherein the dividingwall has a lower end attached to a bottom of the stripping column andthe dividing wall has an upper end that is spaced apart from the top ofthe stripping column. An embodiment of the invention is one, any or allof prior embodiments in this paragraph up through the sixth embodimentin this paragraph wherein the second stripping section is in downstreamcommunication with the hydrocracking reactor and the saturation reactor.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing, all temperatures are set forth in degrees Celsius and,all parts and percentages are by weight, unless otherwise indicated.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

The invention claimed is:
 1. A process to produce diesel comprising:hydrotreating a hydrocarbonaceous feedstock with hydrogen in ahydrotreating reactor over a hydrotreating catalyst at conditionseffective to produce a hydrotreated stream; stripping light gases fromsaid hydrotreated stream to provide a stripped hydrotreated stream;saturating aromatics in said stripped hydrotreated stream to produce asaturated stream; stripping light gases from said saturated stream toprovide a stripped saturated stream; fractionating said strippedsaturated stream to produce a diesel stream; hydrocracking a hydrocarbonstream with hydrogen in a hydrocracking reactor over a hydrocrackingcatalyst at conditions effective to produce a hydrocracked stream;stripping light gases from said hydrocracked stream and said saturatedstream together to produce a joint stripped stream comprising saidstripped saturated stream; and fractionating said joint stripped streamto produce said diesel stream.
 2. The process of claim 1, furthercomprising isolating liquid in said hydrotreated stream from liquid insaid saturated stream while stripping light gases from said hydrotreatedstream and stripping light gases from said saturated stream furthercomprising hydrocracking a hydrocarbon stream with hydrogen in ahydrocracking reactor over a hydrocracking catalyst at conditionseffective to produce a hydrocracked stream.
 3. The process of claim 2,further comprising stripping light gases from said hydrotreated streamand stripping light gases from said saturated stream in a singlestripping column.
 4. The process of claim 3, wherein said singlestripping column includes a dividing wall and said hydrotreated streamis fed to a first side of said dividing wall in said dividing wallcolumn and said saturated stream is fed to a second side of saiddividing wall.
 5. The process of claim 2, further comprising strippingsaid hydrotreated stream with a first stripping stream and strippingsaid saturated stream with a second stripping stream that does notcommunicate with said first stripping stream before said secondstripping stream strips said saturate stream.
 6. The process of claim 1,further comprising hydrotreating said hydrocarbonaceous feed at apressure of about 9 MPa to about 11.0 MPa (gauge).
 7. The process ofclaim 1 producing an unconverted oil stream in said fractionation stepto provide said hydrocarbon stream.
 8. A process to produce dieselcomprising: hydrotreating a hydrocarbonaceous feedstock with hydrogen ina hydrotreating reactor over a hydrotreating catalyst at conditionseffective to produce a hydrotreated stream; stripping light gases fromsaid hydrotreated stream to provide a stripped hydrotreated stream;saturating aromatics in said stripped hydrotreated stream to produce asaturated stream; hydrocracking a hydrocarbon stream with hydrogen in ahydrocracking reactor over a hydrocracking catalyst at conditionseffective to produce a hydrocracked stream; and stripping light gasesfrom said saturated stream and said hydrocracked stream to provide ajoint stripped stream comprising a stripped saturated stream and astripped hydrocracked stream.
 9. The process of claim 8, furthercomprising fractionating said joint stripped stream to produce a dieselstream.
 10. The process of claim 9, further comprising isolating liquidin said hydrotreated stream from liquid in said saturated stream andsaid hydrocracked stream while stripping light gases from saidhydrotreated stream and stripping light gases from said saturated streamand said hydrocracked stream.
 11. The process of claim 10, furthercomprising stripping light gases from said hydrotreated stream andstripping light gases from said saturated stream and said hydrocrackedstream in a single stripping column.
 12. The process of claim 11,wherein said single stripping column includes a dividing wall and saidhydrotreated stream is fed to a first side of said dividing wall in saiddividing wall column and said saturated stream is fed to a second sideof said dividing wall.
 13. The process of claim 9, further comprisingproducing an unconverted oil stream in said fractionation step toprovide said hydrocarbon stream.
 14. The process of claim 8, furthercomprising stripping said hydrotreated stream with a first strippingstream and stripping said saturated stream and said hydrocracked streamwith a second stripping stream that does not communicate with said firststripping stream before said second stripping stream strips saidsaturate stream and said hydrocracked stream.
 15. The process of claim8, wherein light gases stripped from said hydrotreated streamcommunicate with light gases stripped from said saturate stream and saidhydrocracked stream.
 16. A process to produce diesel comprising:hydrotreating a hydrocarbonaceous feedstock with hydrogen in ahydrotreating reactor over a hydrotreating catalyst at conditionseffective to produce a hydrotreated stream; stripping light gases fromsaid hydrotreated stream to provide a stripped hydrotreated stream;saturating aromatics in said stripped hydrotreated stream to produce asaturated stream; hydrocracking a hydrocarbon stream with hydrogen in ahydrocracking reactor over a hydrocracking catalyst at conditionseffective to produce a hydrocracked stream; stripping light gases fromsaid saturated stream and said hydrocracked stream to provide a jointstripped stream comprising a stripped saturated stream and a strippedhydrocracked stream; and fractionating said joint stripped stream toproduce a diesel stream.
 17. The process of claim 16, further comprisingproducing an unconverted oil stream in said fractionation step toprovide said hydrocarbon stream.